1. Field of the Invention
The present invention relates to a pressure control system for an electromagnetic reciprocating pump, and particularly to a pressure control system for an electromagnetic reciprocating pump which can maintain the actual outlet pressure at a predetermined value. 2. Description of the Prior Art
Various proposals have so far been made to the structure of a compressor equipment. But, it is general to convert a rotating drive source to the linear reciprocating motion of a compressor piston through a crank mechanism, or to generate a pressurized fluid by connecting a rotating drive source to a rotation-type fluid compressing device. The former is accompanied by a large noise and vibration, and the overall structure becomes complex. The latter is excellent in noise and vibration, but the sealing is very difficult in the rotation-type fluid compressing device.
Also, outlet pressure control for these compressor equipments is typically on-off control, and it is difficult to perform an accurate pressure control with high precision.
In contrast to this, in an electromagnetic reciprocating pump using an electromagnetic drive means as the drive source, since the electromagnetic drive means itself performs a linear motion, a mechanism for converting a rotary motion to a linear motion or an advanced sealing technique such as needed in the rotation-type fluid compressing device is not required, so it has advantages such as simplification of the structure of the whole equipment and a smooth fluid compressing motion.
In addition, different from the compressor equipments of other types as described above, it is extremely easy to vary the piston stroke in the electromagnetic reciprocating pump. That is, the piston stroke of the electromagnetic reciprocating pump directly connected to the electromagnetic drive means can be varied with a relation of 1:1 by controlling the amplitude and/or frequency of the AC current to be supplied to the excitation winding of the electromagnetic drive means to vary its motion stroke. This is another advantage of the electromagnetic reciprocating pump.
Electromagnetic drive means suitable for the electromagnetic reciprocating pump is described in Maurice Barthalon's U.S. Pat. No. 3,542,495, for instance.
As described above, the electromagnetic reciprocating pump has many advantages as compared with other type compressor equipments, but no proposal was made in the past to the pressure control of its discharge fluid.